The invention relates to novel catalysts for hydrocarbon conversion processes, particularly aromatic saturation processes.
In the refining of hydrocarbon-containing feedstocks, it is often necessary to convert hydrocarbon compounds contained in the feedstock to different forms. Typically, particulate catalysts are utilized to promote chemical reactions when feedstocks contact such catalysts under hydrocarbon conversion conditions to produce economically or environmentally upgraded hydrocarbon products. During the course of catalytic refining of hydrocarbons, heterocyclic compounds, including oxygen, nitrogen and sulfur compounds, are removed from hydrocarbon-containing feedstocks. Aromatic compounds contained in a feedstock contact a catalyst in the presence of hydrogen, causing conversion of such aromatic compounds to more saturated forms, i.e., the aromatic compounds are hydrogenated.
An on-going aim of the art is to provide a catalyst having suitably high activity and stability. Activity may be determined by comparing the temperature at which various catalysts must be utilized under otherwise constant processing conditions with the same feedstock so as to produce a given percentage of a given product. The lower activity temperature for a given catalyst, the more active such a catalyst is in relation to a catalyst of higher activity temperature. Alternatively, activity may be determined by comparing the percentages of conversion of feedstock reactants to a given product when various catalysts are utilized under otherwise constant processing conditions with the same feedstock. The higher the percentage of product converted to the given boiling range for a given catalyst, the more active such a catalyst is in relation to a catalyst converting a lower percentage of the same feedstock reactants to the same product. As a catalyst deactivates during processing, its stability is generally measured in terms of the change in temperature required per unit of time to maintain a given percentage of product, or alternatively, in terms of the change in percentage of product per unit of time. The lower the change in percentage of product per time unit for a given catalyst, the more stable such a catalyst is in relation to a catalyst yielding a greater change.
Recent legislation has increased the demands for refiners to reduce the content of environmentally undesirable aromatic-containing compounds in fuel products such as diesel fuels. Catalytic aromatic saturation is a useful refining process for such reduction. Aromatic saturation involves the conversion of relatively unsaturated hydrocarbon compounds, including aromatic-containing compounds, into environmentally acceptable more saturated hydrocarbon-containing product compounds. Several hydrotreating catalysts have been utilized for such operations. A typical catalyst contains hydrogenation metals supported on a porous refractory oxide. Such a catalyst provides suitable aromatic saturation activity (i.e., percentage conversion of aromatic compounds to products containing a greater hydrogen to carbon ratio, e.g. more saturated products); however, the search continues for catalysts providing improved activity and stability.